JPH02284548A - Communication system - Google Patents

Abstract

PURPOSE:To secure transmission reliability almost similar to a conventional example without losing information which a pulse position has by transmitting and receiving a signal having information on the pulse position though chirp conversion. CONSTITUTION:The output of a pulse position modulator 1 is inputted to a balance modulator 2, and is converted into a waveform appropriate for converting the signal which has been pulse position-modulated into a chirp signal, is inputted to an expansion chirp converting element 3. Then, prescribed band components are expanded in the direction of a time base, and are outputted to a transmission line through an amplifier A. The signal received from the transmission line on the other hand is inputted to a compression chirp converting element 4, and the chirp signal is inversely converted into a pulse position modulation wave and it is inputted to a pulse position demodulator 5. It inversely converts the balance modulator 2 on a transmission-side and it demodulates the pulse position modulation wave into an original analogue or digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a communication system, and particularly to a communication system in which input signals are transmitted and received through predetermined modulation and demodulation processing.

[Prior Art] Conventionally, when converting binary digital signals of "1" and "O" into predetermined codes and transmitting and receiving them, as shown in FIG. 11(a), "l" and "o" are A modulation method in which the chirp conversion element 31 corresponds to the presence or absence of a chirp signal cs to a binary digital signal, or a modulation method that corresponds to the presence or absence of a chirp signal cs as shown in FIG. 11(b).
”, chirp conversion element 31 into binary digital signals of “o”
．． Chirp signal c with different patterns depending on 41
s1. A modulation method that supports csO is known.

The right side of FIG. 1I (a) and (b) shows the modulated signals formed by the above method, and the chirp signals cs, cs
1. The cso is an input signal (rectangular wave pulse) whose frequency components are expanded in the time axis direction by the chirp conversion element 31 or 41 using different expansion characteristics. In particular, in FIG. 11(b), the chirp conversion element 31.
41 respectively form chirp signals csl and csO, and by adding them, the output signal on the right side of the figure is obtained.

[Problems to be Solved by the Invention] Of the two conventional examples described above, in the method shown in FIG. 11(a), the presence or absence of a chirb signal corresponds to the codes "1" and "0" of the digital signal. Code "1" and "0"
There are uncertainties in the separation and identification of
There was a possibility that the code "0" would be determined as "1" due to the influence of noise on the transmission path.

In order to solve this problem, a method as shown in Figure 11(b) was devised, but as is clear from the figure, this method requires chirb conversion elements with different conversion patterns, and also Of course, since an inverse conversion element capable of detecting multiple patterns of chirp signals is required on the
There is a problem in that the circuit structure tends to be more complex, larger, and more expensive than the method shown in FIG. 3(a).

SUMMARY OF THE INVENTION An object of the present invention is to solve the following two problems and to provide a communication system that can perform reliable information transmission using Chilb signal conversion with a simple and inexpensive configuration.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, in a communication system in which an input signal is transmitted and received through predetermined modulation/demodulation processing, the input signal is transmitted and received on the transmitting side using a pulse position modulation method. The frequency components of this modulated signal are each expanded in the time axis using different expansion characteristics to form a chirb signal and transmitted. On the other hand, on the receiving side, the frequency components of the received chub signal are modulated by the different expansion characteristics. We adopted a configuration in which the original signal is reproduced by compressing it using compression characteristics that are inverse characteristics corresponding to the expansion characteristics, and then performing pulse position demodulation.

[Function] According to the above configuration, an input signal is converted into a pulse position modulated chirb signal having a frequency/time characteristic called tangent and is transmitted, while on the receiving side, the received chirb signal is inversely converted and then pulsed. The original signal can be reproduced by position demodulating.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIGS. 1(a) and 1(b) illustrate the basic structures of a transmitting device and a receiving device adopting the present invention, respectively.

In FIG. 1(a), reference numeral 1 denotes a pulse position modulator that modulates the pulse position of a series pulse representing a manually inputted analog signal or a binary digital signal.

The output of the pulse position modulator l is input to a balanced modulator 2, which is suitable for efficiently converting the pulse position modulated signal generated by the pulse position modulator 1 into a chirp signal. Convert to a waveform.

The output of the balanced modulator 2 is inputted to an expansion Chilb conversion element 3, and a predetermined band component thereof is expanded in the time axis direction.

The output of the expansion chirp conversion element 3 is outputted to the transmission line via the amplifier A.

On the other hand, in FIG. 1(b), the signal received from the transmission path (output of the circuit in FIG. 1(a)) is amplified to a predetermined level by amplifier A, and then input to the compression Chilb conversion element 4. be done. The compression chirb conversion element 4 inversely converts the chirb signal into a pulse position modulated wave, and its output is input to the pulse position demodulator 5 .

The pulse position demodulator 5 performs inverse conversion of the balanced modulation 2 on the transmission side, and demodulates the pulse position modulated wave into the original analog or digital signal.

2 and 3 illustrate the modulation and demodulation operations of the pulse position modulator 1 and the pulse position demodulator 5 shown in FIGS. 1(a) and 1(b), respectively.

First, the pulse position modulation operation of the pulse position modulator 1 will be explained.

In FIG. 2, reference numeral a indicates an input signal manually input to the pulse position modulator 1. In FIG. Here, for ease of explanation, an analog signal is shown as the input signal of the pulse position modulator l.

In FIG. 2, symbol A is a sawtooth wave generated by an oscillator built in the pulse position modulator 1, and a waveform of symbol C is obtained by adding this sawtooth wave and Kerr's manual waveform.

Next, using a comparison circuit inside the pulse position modulator l, a predetermined slice level and a signal of code C are compared to obtain a signal d.

Furthermore, after passing the signal d through a differentiation circuit built in the pulse position modulator l to obtain a signal e, this is compared with a predetermined slice level by a comparison circuit different from the above, and then amplified.
A signal f that becomes high level when the level of the signal e is higher than the slice level is obtained.

Next, the demodulation operation of the pulse position demodulator 5 will be explained.

In FIG. 3, symbol a is a signal pulse position modulated by the above procedure, and this signal is added to an inverse sawtooth wave such as symbol A output from the oscillator built in the pulse position demodulator 5, and the signal a is get.

Subsequently, when the signal C is clipped by a predetermined clip level, a pulse amplitude modulated signal as shown by code d is obtained. By passing this signal d through a low-pass filter, the original signal shown by the broken line can be obtained.

Figure 4 shows different pulse position modulation and demodulation methods.
The pulse position modulation and demodulation processing that can be applied when the input signal is a digital signal is shown.

In Fig. 4, symbol a is a manually inputted serial binary digital signal, and by taking in this signal one bit at a time and cumulatively adding it, the data signal (summation signal) shown in Fig. 4(b) is obtained.
get b. During accumulation, only one bit of the last digit is used as a signal.

Furthermore, set one time slot as shown by the dashed line,
The pulse position modulation waveform C can be obtained by generating short pulses in the first half or the second half of the time slot, respectively, depending on the binary value of the signal "l" or "0".

On the other hand, when a modulated waveform of code C is input, based on the time slot signal generated in synchronization with this signal,
It is possible to determine whether the short pulse occurs in the first half or the second half of the slot, and obtain the signal d.

Further, this signal d is delayed by one time slot to obtain a signal e, and by performing phase detection using the signals d and e, a demodulated signal f can be obtained.

Next, the structure of the chirp conversion element of the transmitter/receiver is shown.

FIGS. 5(a) to 5(e) show examples of the configuration of the chirp conversion element 3 on the transmitting side.

The chirp conversion element 3 includes a comb-shaped electrode (hereinafter referred to as I) on a piezoelectric substrate 33c having a piezo effect as shown in FIG. 5(a).
When an electric signal is applied to the IDT 33a of the signal input section, mechanical vibration is generated due to the piezoelectric effect, and the surface waves of the vibration are transmitted to the substrate 3.
Propagates on 3c.

When this surface wave reaches the IDT 33b of the output section, it is converted into an electric signal again. The output-side IDT 33b generates an electrical signal in tune with the vibration frequency determined by the electrode spacing, but as shown in the figure, the spacing of the output-side IDT 33b changes densely as it moves away from the human-powered IDT 33a, so the output signal varies depending on the frequency. Different delay times.

That is, different frequency components in the signal are separated in time. The output amplitude and delay characteristics with respect to the human input frequency of this extension chirp conversion element are shown in Figures 5 (b) and (C).
It looks like this. That is, at least the frequency f1
The frequency characteristics are flat in the region from to f2,
On the other hand, due to the electrode arrangement described above, the delay time increases linearly from frequency fl toward r2 (tl to t2.).

Therefore, from fl to f2
When a rectangular wave pulse-like signal as shown in Fig. 5(d) containing a high frequency component with a spectral component spread between The signal is expanded into a waveform (chirp signal) that continuously changes from fl to f2 and is output.

On the other hand, the compression chirp conversion element 4 in FIG. 1(b) is different from the expansion/contraction chirp conversion element 3 as shown in FIG. 6(a).
Since the density of the DT43a and DT43b is reversed, the amplitude characteristics are the same as those of the decompression chirp conversion element as shown in Fig. 6(b), but the amplitude characteristics are different from the frequency fl as shown in Fig. 6(C). The delay characteristics are reversed between f2.

Therefore, for the input of the chirp signal generated by the expansion chirp conversion element 3 whose frequency changes continuously from fl to f2 during the time interval tl to t2 as shown in FIG. A pulse signal as shown in Figure (e) is reproduced.

The input signal to the expansion chirb conversion element in FIG. 5 is, for example, a single pulse wave with a pulse width of 1/H multiplied by a signal with a frequency fO as shown in FIG. It has spectral components as shown in FIG. 5(b) or FIG. 6(b).

On the other hand, the conversion profit from chirb signal to pulse signal 1-I is -f yab (13-J- product of duration and bandwidth (BT
product). The BT product is usually much larger than 1. For example, if B = 10 MHz and T = 20 ns, then BT = 200, and the chirb signal will be compressed into a pulse signal with a peak power that is BT times its power.
The S/N ratio will be significantly improved.

In information transmission, first, the pulse position modulator 1 of the transmitting device shown in FIG. After obtaining the signal, convert it to a chirb signal, and use the receiver shown in Figure 1 (b) to perform pulse position demodulation using the waveform inversely converted from the chirb signal to a pulse position modulated wave to reproduce the original analog signal or digital signal. become.

In particular, in the modulation and demodulation processing of chirp signals, the pulse signal is chirp-converted based on the amplitude and delay characteristics of the output with respect to the input 144 frequency of the chirp conversion element as shown in FIGS. 5 and 6 (b) and (C). Even if the pulse is later converted back to the original pulse (l'3'), the information of the pulse position is not lost, so there is no risk of one of the binary information changing; It is possible to ensure transmission reliability that is almost the same as or better than the example in which different chirp signals are assigned to value signals.

In addition, since the compression chirp conversion element on the receiving side detects a match with the same pattern as the characteristics of the element, the chirp signal is Even if the signals are superimposed on the second axis, demodulation is possible without any problem.

As shown above, according to the above embodiment, information can be reliably transmitted using a simple and inexpensive configuration using a single chirp conversion means in the transmitter/receiver device without being affected by disturbances such as noise. .

In the above embodiment, only the signal modulation/demodulation section is shown, but it goes without saying that this system can be applied to both wired and wireless communications. Additionally, by using a device that converts electrical signals into optical signals (E10 conversion) and a device that converts optical signals into electrical signals (0/E conversion), this method can also be applied to optical communications. .

FIG. 8 shows an application example of this system, which is an example of a communication system using an optical fiber as a transmission path. In the figure, numeral 6 is an IE/0 converter using a semiconductor laser element, etc., and numeral 7 is a P
An O/E converter using an IN foot diode or the like, and reference numeral 8 indicates an optical fiber. According to such a configuration, as described above, it is possible to mainly improve the reception S/N ratio,
Becomes able to communicate over long distances. In FIG. 8, reference numeral 81 indicates the transmitting side circuit of FIG. 1(a), and reference numeral 82 indicates the receiving side circuit of FIG. 1(b).

FIG. 9 shows an example in which this method is applied to optical beam communication. In the figure, reference numeral 6 is an E10 consisting of a semiconductor laser element, etc.
The converter 7 is an O/E converter made of a PIN photodiode or the like, and 9 is a light beam. With such a configuration, especially in the case of long-distance optical beam communication of less than 1 km, it is strongly affected by signal attenuation and fluctuations due to weather conditions such as rainfall, atmospheric fluctuations, and fluctuations in ambient light. Therefore, the reliability of communication can be greatly improved by the effect of removing disturbance disturbances in this method. In FIG. 9, reference numeral 81.
Similarly to FIG. 8, 82 indicates the transmitting side and receiving side circuits of FIGS. 1(a) and 1(b), respectively.

Furthermore, the configuration of FIG. 9 can also be used for light diffusion communication as shown in FIG. 1O. In Figure 1O, the light emitting part of the E10 converter on the transmitting side uses a suitable optical system to illuminate the diffused light.
It is configured to project O. The diffused light is received by a plurality of receiving devices similar to those shown in FIG. 9 as shown.

With such a configuration, it is possible to expand the reception range using diffused light. In addition, the optical signal received by the receiving device becomes weak due to this light diffusion, but as mentioned above, the reliability of code identification is improved by the conversion gain obtained during chirp inverse conversion, so when using the same transmission power as the conventional example. However, transmission reliability can be further improved.

[Effects of the Invention] As is clear from the following, according to the present invention, in a communication system in which an input signal is transmitted and received through predetermined modulation/demodulation processing, the input signal is modulated by a pulse position modulation method on the transmitting side. , the frequency components of this modulated signal are expanded in the time axis using different expansion characteristics to form and transmit a chirp chirp signal, while on the receiving side, the frequency components of the received chirp signal are expanded in the different expansion characteristics as described above. The structure is such that the original signal is reproduced by compressing it using the compression characteristic of the inverse characteristic corresponding to each characteristic, and then performing pulse position demodulation. On the receiving side, the received chirp signal is inversely converted and then pulse position demodulated to reproduce the original signal.

In particular, since signals with information on pulse positions are transmitted and received via chirp conversion, the information on pulse positions is not lost. Similar transmission reliability can be ensured.Additionally, the advantage of using chirp transform is that it has high code discrimination ability, and during demodulation, chirp signal compression causes an apparent increase in signal power, improving the S/N ratio. In particular, communication reliability can be ensured even if there are restrictions such as transmission power limitations on the transmission path or large amounts of disturbance noise. Can be mentioned.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram showing the structure of a transmitting side device according to the communication method of the present invention, FIG. 1(b) is a block diagram showing the structure of a receiving side device according to the communication method of the present invention, and FIG. The figure is a waveform diagram showing the pulse position demodulation operation in the configuration of Figure 1 (a), Figure 3 is a waveform diagram showing the pulse position demodulation operation in the configuration of Figure 1 (b), and Figure 4 is a waveform diagram showing the pulse position demodulation operation in the configuration of Figure 1 (b). Waveform diagram showing signal pulse position modulation and demodulation method, 5th
Figures (a) to (e) and Figures 6 (a) to (e) are explanatory diagrams showing the structure and characteristics of the chirp conversion element for expansion and compression, respectively, and Figure 7 is a large caballus to the chirp conversion element. Waveform diagrams showing waveforms, FIGS. 8 to 10 are block diagrams showing different embodiments of the communication system of the present invention, and FIGS.
b) is an explanatory diagram showing different traffic methods. 1--Pulse position modulator 2-Balance modulator 3...-
Chirp conversion element for expansion 4 - Chirp conversion element for compression 5 - Pulse position demodulator 6 - E10 converter 7 - O/E converter 8 -
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Claims (1)

[Claims] 1) In a communication system in which an input signal is transmitted and received through predetermined modulation/demodulation processing, the input signal is modulated by a pulse position modulation method on the transmitting side, and the frequency components of the modulated signal are each modulated with different expansion characteristics. On the receiving side, the frequency components of the received chirp signal are compressed using the inverse compression characteristics corresponding to the different expansion characteristics, and then A communication method characterized by reproducing the original signal by performing pulse position demodulation.